Table of Content

25 January 2021, Volume 60 Issue 1-2
LUO Jun, AI Linghao, AI Yanli...
2021, 60(1-2):  1-19.  doi:10.13471/j.cnki.acta.snus.2020.12.23.2020B154
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The TianQin project aims to launch and deploy around 2035 an equilateral triangular constellation with each side measuring 170 000 kilometers，forming a gravitational wave observatoryTianQin. TianQin aims to detect gravitational waves in the frequency range 10-4~1 Hz and to draw a more comprehensive picture of the universe for mankind. In this articlewe introduce the background and the proposing processthe major gravitational wave sources and scientific objectivesthe key technology problems to be solvedthe technology roadmapand the current progress of the TianQin projectso as to facilitate more people to join in this challenging and exciting work.

The merger of binary massive black holes and the detection capability with TianQin
Yiming HU, Qingwen WU, Weihua LEI, Yan WANG, Yang WANG, Yanli AI, Rongfeng SHEN, Yuanchuan ZOU, Shangfei LIU, Weipeng LIN, Xiao FAN, Wenfan FENG, Haitian WANG, Jianwei MEI
2021, 60(1-2):  20-30.  doi:10.13471/j.cnki.acta.snus.2020.11.11.2020B130
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Observations have shown that at the center of most galaxy there is a supermassive black hole of millions to billions solar masses， together with a large amount of stellar mass black holes. At the same time， evidence of the existence of intermediate-mass black holes is also emerging. Within hundreds of millions of years after the formation of the universe， some supermassive black holes reached tens of billions of solar masses. The formation and growth of these supermassive black holes is still a mystery. In the hierarchical structure model of galaxy formation， small galaxies are constantly merging to form larger and larger galaxies， and the black holes at the center of galaxies also undergo a process of merger and accretion， gradually forming supermassive black holes at different redshifts. This article summarizes the basic characteristics of black holes， current observation results， intermediate-mass black hole candidates， seed black holes， and the relationship between supermassive black holes and galaxies. The detection capability with the TianQin observatory is also evaluated. The analysis of the gravitational waves of these massive black hole binaries will greatly help us to understand the characteristics of massive black holes in the universe and the history of formation and evolution of supermassive black holes.

The gravitational wave source of extreme-mass-ratio insprials and its detection
Huimin FAN, Yiming HU, Tieguang ZI
2021, 60(1-2):  31-40.  doi:10.13471/j.cnki.acta.snus.2020.11.05.2020B116
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Extreme-mass-ratio inspirals are systems consisting of a massive black hole （MBH） and a stellar-origin compact object （CO）. It has great scientific significance， such as testing general relativity and exploring the black hole nature. In this paper， we describe the formation picture， the scientific value， and the current research of EMRIs，and through calculating the EMRI rate and parameter estimation， we get the detectability of TianQin on EMRIs. We find that TianQin can observe EMRIs up to redshift $z～2$. We also find that EMRI detections could reach tens or hundreds per year in the most optimistic astrophysical scenarios. Intrinsic parameters are expected to be recovered to within fractional errors of $～10-6$， while typical errors on the luminosity distance and sky localization are 10% and 10 $?deg2,??$respectively. EMRIs can also be used to constrain possible deviations from the Kerr quadrupole moment to within fractional errors$～10-4$.

Stellar-mass binary black holes： Inspirals and their detection
Pakhin TAM, Ziwei OU, Shuai LIU, Weihua LEI, Yiming HU
2021, 60(1-2):  41-52.  doi:10.13471/j.cnki.acta.snus.2020.11.14.2020B134
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According to stellar evolution theory， an evolved massive star will eventually become a compact object such as a neutron star or a black hole. On the other hand， local density fluctuations in the early Universe could also form primordial black holes of stellar mass. Since the dawn of the Universe， stellar-mass black holes （SBHs） can come together to form binaries through mechanisms such as coevolution and dynamical processes. Before ground-based gravitational wave （GW） detectors made their first successful cosmic detections， the mass of SBHs had been measured by electromagnetic waves only， and never exceeded around 15 solar masses. The LIGO/Virgo detection of GWs from binary SBH mergers has drawn the attention of many scientists， in particular， the GW signals resulting from the inspirals of binary SBHs should be detectable by space-borne GW detectors. Based on the number of GW events using ground-based detectors， it is expected that TianQin will be able to detect a few to dozens of GW events related to inspirals of binary SBHs. Given the long expected duration for each inspiral event， such signals can help to adequately measure parameters including the expected merger time （down to ~1 second） and the exact location of the SBH （down to 1 square degree）. The inspiral through merging of binary SBHs will provide excellent astrophysical probes for multi-frequency GW observations.
Stochastic backgrounds of gravitational wave and the detectability at TainQin
Yun JIANG, Zhengcheng LIANG, Yiming HU, Dongdong WEI
2021, 60(1-2):  53-61.  doi:10.13471/j.cnki.acta.snus.2020.11.14.2020B135
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Near the milli-Hertz band there are stochastic gravitational wave background （SGWB） that can be generated from numerous sources， such as the primordial universe and the incoherent superposition of gravitational waves from astronomical sources. Given the strongest detectability for the SGWB at the order of the milli-Hertz frequencies， space-borne detectors of gravitational waves （e.g. TianQin） will help us to explore the origin of our universe， and it may also become a unique and efficient approach for probing new physics beyond the Standard Model. In this article we will discuss the production mechanism for various SGWBs and briefly assess the detectability for the SGWB at the TianQin.

Research on Tianqin's capability of probing the cosmic expansion
Xiaodong LI, Xiaoyuan XIAO, Lingfeng WANG, Zewei ZHAO, Xin ZHANG
2021, 60(1-2):  62-73.  doi:10.13471/j.cnki.acta.snus.2020.11.18.2020B143
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After decades of development， the research of cosmology has entered the epoch of precision cosmology. According to the Planck observational results and the ΛCDM model， we need only 6 parameters to reproduce the evolution history of the universe which is consistent with the observed data in a statistical sense. However， in fact， there are still many unsolved important scientific problems in the field of cosmology， and there will be some inconsistencies in different observational data when inferring cosmological parameters based on the basic ΛCDM model. The answers to these questions require extension of the basic ΛCDM model and accurately measurements of the additional parameters. At present， the mainstream cosmological probes are mainly optical （and near-infrared） observations of the expansion history and structural growth of the universe， so they may have similar systematic errors. It is very important for the future research of cosmology to develop new non-optical observational probes. Because the amplitude of gravitational wave carries the information of absolute luminosity distance， it can help us to establish the real distance-redshift relation and study the expansion history of the universe. This observation of gravitational waves is known “standard siren”. Cosmological research is one of the important research objectives of the Tianqin space gravitational wave detector， which is expected to be able to observe a large number of gravitational wave events in the future， providing valuable observational data for the study of cosmology （especially at high redshift）. In this paper， we introduce previous researches about the ability of Tianqin standard siren data to constrain the cosmological parameters. We consider pop Ⅲ， Q3nod and Q3d models. The results show that for different binary models of massive black holes， the Tianqin project yields to different constraining results on the cosmological parameters， and the Q3nod model has the strongest ability. The standard siren detection of Tianqin is helpful to break the degeneracy of cosmological parameters caused by other observation methods， so as to effectively improve the measurement accuracy of cosmological parameters. We have reason to believe that the future gravitational wave observations combined with optical and radio observations will promote the exploration of the history of cosmic expansion to a new level， and provide help to detect the size of Hubble constant and reveal the nature of dark energy.

Probing the nature of gravity and black hole with TianQin
Jiandong ZHANG, Jiahui BAO, Yiming HU, Mujie JI, Changfu SHI, Ning XIE, Tieguang ZI, Jianwei MEI
2021, 60(1-2):  74-85.  doi:10.13471/j.cnki.acta.snus.2020.11.09.2020B122
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An important objective of space borne gravitational wave detectors is using gravitational wave signals to probe the fundamental theories of physics. Specifically， it means the study of the nature of gravity and black holes. The former objective is to test whether the gravitational theory is general relativity or not， and the latter one is to test whether the detected compact obejcts radiating gravitational waves is the Kerr black hole predicted in general relativity. As a space borne gravitational wave detector， TianQin may detect a lot of signals from many different kinds of gravitational wave sources. Using these signals， we expect to probe the nature of gravity and black holes from all possible aspects. In this article， we will introduce the methods that TianQin would use to probe the nature of gravity and black holes， and analyze the expected detection accuracy of TianQin.

Test of gravity with gravitational waves
Qing GAO, Yungui GONG, Jiang LONG
2021, 60(1-2):  86-98.  doi:10.13471/j.cnki.acta.snus.2020.10.30.2020B110
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Gravitational waves （GWs） in Einstein’s general relativity propagate with the speed of light， and they have two polarizations. In modified gravitational theories beyond general relativity， GWs may have up to six polarizations， the speed of propagation may not be the speed of light， graviton may be massive and there may exist dipole radiation. In this paper， we discuss the properties of GWs and how to use the measurement of GWs to test theories of gravity.

Introduction of templates for low-frequency gravitational waves
Shucheng YANG, Wenbiao HAN
2021, 60(1-2):  99-111.  doi:10.13471/j.cnki.acta.snus.2020.11.06.2020B118
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Matched filtering is critical in the detection and parameter estimation of gravitational waves （GWs）. The application of matched filtering requires waveform templates， which are lots of GW waveforms from theoretical calculations. Space-borne GW detectors aim at low-frequency GWs. These signals have long timescales， ranging from several days to several years， and require theoretical waveforms with high accuracy. Moreover， some low-frequency GW sources have complicated configurations， such as large eccentricities and precession， which leads to a large parameter space of waveforms， and numerous templates are required. Therefore， comparing with ground-based GW detection， space-borne GW detection requires more efficiency and quality for most waveform templates. In this paper， we first review some waveform templates of primary low-frequency GW sources （supermassive binary black holes， extreme-mass-ratio inspirals， and compact binary stars in the Galaxy）. Then we summarize the characteristics of these templates and look into the future of the research for low-frequency GW astronomy.

Techniques for gravitational wave data analysis
Yiming HU, Zhengcheng LIANG, Huimin FAN
2021, 60(1-2):  112-122.  doi:10.13471/j.cnki.acta.snus.2020.11.05.2020B117
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Space-borne gravitational wave detection has been the research focus and hotspot for the field of astronomy and physics and will continue to be so. The scientific goal of space-borne gravitational wave missions must be achieved through data analysis. Therefore， to carry out data processing research combined with actual space-borne gravitational wave detectors is an important premise for achieving the scientific goal of space-borne gravitational wave missions. We based on the space-borne gravitational wave missions TianQin and introduce the concept of matched filtering in gravitational wave data analysis. Furthermore， we introduce some basic concepts related to gravitational wave signal detection and parameter estimation.

Orbit and constellation design for TianQin： progress review
Xuefeng ZHANG, Bobing YE, Zhuangbin TAN, Huimin YUAN, Chengjian LUO, Lei JIAO, Defeng GU, Yanwei DING, Jianwei MEI
2021, 60(1-2):  123-128.  doi:10.13471/j.cnki.acta.snus.2020.11.02.2020B112
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The TianQin project plans to deploy three drag-free controlled satellites in circular high Earth orbits at an altitude of 105 km. The satellites form a nearly equilateral-triangle constellation， and exchange high-precision laser interferometric links to detect low-frequency gravitational waves in the mHz frequency band. TianQin features a geocentric concept， and is facing the challenge of designing and utilizing high Earth orbits to the best effect. In this paper， we briefly summarize the main progresses on TianQin’s orbit and constellation design， including constellation stability optimization， orbital orientation and radius selection， the Earth-Moon’s gravity disturbance evaluation， and eclipse avoidance.

The spacecraft system and platform technologies for gravitational wave detection in space
Lihua ZHANG, Ming LI, Yongxin GAO, Yuexin HU, Fengbin WANG, Tao ZHANG
2021, 60(1-2):  129-137.  doi:10.13471/j.cnki.acta.snus.2020.11.14.2020B133
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The detection of gravitational wave is a leading edge scientific research area in contemporary physics. Compared to the detection on the ground， the space based gravitational wave detection can explore richer gravitational wave sources and more distant objects， and so is considered to be of great scientific value. The detection of gravitational wave in space brings great technical challenges and presents demanding technical requirements for the spacecraft system and platform. Traditional platforms can not meet the mission requirements. The ultra-quiet and ultra-stable platform has to be developed. A series of critical technologies need to be broken through. This paper analyzes the technical challenges and constraints faced by the spacecraft system and platform for gravitational wave detection. The preliminary spacecraft system design concept for TianQin gravitational wave detection mission， including spacecraft configuration and layout， is proposed. The critical technologies for spacecraft platform are also analyzed and solution approaches are suggested.

External heat flux and thermal control design of space gravitational wave detection satellite
Bing XIA, Houyuan CHEN, Yiping WANG, Jiajian PAN, Weigang BAI, Wenbo CHANG, Yanwei DING
2021, 60(1-2):  138-145.  doi:10.13471/j.cnki.acta.snus.2020.11.11.2020B131
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The external heat flux is one of the important factors affecting the space gravitational wave detection satellite. In this paper， the β angle and external heat flux of the heliocentric and geocentric gravitational wave detection satellites are summarized， and the variation characteristics of the external heat flow are analyzed. The gravitational wave satellite adopts the thermal design principle of passive thermal control， supplemented by active thermal control. The thermal design of the whole satellite and the key payload （e.g. space telescope） is carried out. At the same time， flexible support structure is adopted to solve the thermal deformation problem of the structure to ensure the stability of the substructure. Finally， the thermal simulation of gravitational wave detection satellite is introduced.

Review of high precision temperature sensing， measurement and control technology
Mingxuan WEN, Jue LI, Cheng WANG, Chen LING, Lingyun GU, Yanwei DING
2021, 60(1-2):  146-155.  doi:10.13471/j.cnki.acta.snus.2020.11.11.2020B127
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In space gravitational wave detection， high precision temperature sensing， measurement and control are some of the key technologies for satellites， with high technical requirements and implementation difficulty. This paper mainly focuses on high precision temperature sensing， measurement and control， introducing the sensing characteristics of traditional platinum resistance and NTC thermistor temperature sensors， and new optical fiber temperature sensing and PID temperature control algorithms. The characteristics of temperature sensing， measurement and control algorithms are analyzed and summarized.

Review of formation dynamics and control technology of space-borne gravitational wave detection system
Jihe WANG, Jinxiu ZHANG, Yunhe MENG, Jianing SONG, Lie YANG
2021, 60(1-2):  156-161.  doi:10.13471/j.cnki.acta.snus.2020.11.10.2020B123
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With respect to the challenge of ultra-long-distance formation dynamics and control technology brought by space-borne gravitational wave detection system, this paper investigates and analyzes the research status of dynamics and control technology involved in space-borne gravitational wave detection system, including ultra-long-distance relative dynamics, high stability orbit design, high precision configuration initialization strategy and control method, formation reconfiguration and maintenance, multi degree of freedom coordinated control. Based on the analysis of the research status , the key technologies in dynamics and control of space-borne gravitational wave detection system are proposed, including modeling and analysis of formation divergence mechanism for ultra-long-distance formation, robust optimization design theory and method for high stability configuration, initialization and maintenance technology of high precision configuration with limited orbital maneuverability, formation attitude and orbit maintenance strategy under unscientific and fault mode and multi degree of freedom coordinated control approach.

Inter-satellite laser interferometry
Huizong DUAN, Yingxin LUO, Jingyi ZHANG, Min MING, Hao YAN, Fan ZHU, Qing XIAO, Meng LI, Bin CAO, Tao LI, Zhizhao WANG, Hsienchi YEH
2021, 60(1-2):  162-177.  doi:10.13471/j.cnki.acta.snus.2020.10.30.2020B107
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In recent years， a large number of space missions such as space gravitational wave detection， satellite gravity measurement， deep space exploration and other space missions have put forward extremely challenging technical requirements for ultra-long distance and ultra-high precision inter satellite laser interferometry technology. For example， in typical space gravitational wave detection， it is required to reach the accuracy of Pico-meter（10-12 m） at a distance of one million kilometers （109 m）. According to the typical requirements of intersatellite laser interferometry in space missions， this paper introduces the overall structure of intersatellite laser interferometry system， discusses and discusses the key technologies in the measurement system， such as space applied laser technology， frequency stabilization technology， precise phase measurement and ultra-low power weak light phase locking technology， fast acquisition， tracking and ultra-precision beam pointing of inter satellite laser Measurement and control technology， as well as the current technology development status. The improvement of intersatellite laser interferometry technology will be able to meet the needs of a wider range of space missions and greatly promote the further development of space missions.

Preliminary analysis of space gravitational wave detection telescope system technology
Wengtong FAN, Hongchao ZHAO, Lei FAN, Yong YAN
2021, 60(1-2):  178-185.  doi:10.13471/j.cnki.acta.snus.2020.11.02.2020B111
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In order to realize the detection of gravitational waves in the frequency range of 0.1 mHz~1 Hz， the formations（or constellations） of space gravitational wave detectors such as Tianqin， LISA， and Taiji needs to achieve picometer-level measurement accuracy on the order of hundreds of thousands or even millions of kilometers. Therefore， telescopes directly used as part of the inter-satellite interferometry optical path are facing huge technical challenges. Space gravitational wave detection telescope has the characteristics of ultra-high precision and ultra-high stability. This article takes the LISA gravitational wave detector telescope as the research object， and analyzes the optical design scheme of the telescope according to the requirements of 10 pm/Hz1/2 core index of inter-satellite laser interferometry and the actual demand of gravitational wave detection. And based on the design， analysis and discussion on material selection， optical processing， adjustment and stray light suppression are carried out， which provides a reference for the subsequent development of the telescope.

Preliminary design consideration and development of TianQin inertial sensor
Hongyin LI, Yanchong LIU, Chengrui WANG, Yanzheng BAI, Li LIU, Shuchao WU, Shaobo QU, Dingyin TAN, Hang YIN, Zhuxi LI, Shanqing YANG, Zebing ZHOU
2021, 60(1-2):  186-193.  doi:10.13471/j.cnki.acta.snus.2020.11.21.2020B144
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This work firstly introduces the requirement， principle and development of inertial sensors in gravitational wave detection mission， and focuses on the development of LISA Pathfinder inertial sensors. Compared with the requirements analysis of TianQin project， the design points of TianQin inertial sensor are discussed， and on this basis， the preliminary design and noise analysis of TianQin inertial sensor are given.A preliminary design of the key parameters for the TianQin inertial sensor is then carried out， which are employed to calculate and synthesize the direct perturbations on TM. Finally， the in-orbit performance of TianQin-1 inertial sensors and follow-up research plan is presented.

The developments of micro propulsion technology based on space gravitational wave detection task
Daren YU, Xiang NIU, Taibu WANG, Shangsheng WANG, ming ZENG, Kai CUI, Hui LIU, Liangcheng TU, Zhu LI, Xiangqing HUANG, Jianping LIU, Yan SHEN, Huisheng PENG, Cheng YANG, Peiyi SONG, Shuangyang KUANG, Kai ZHANG, Xiaochen SUO, Xiaobo HUANG, Xuhui LIU, Xudong WANG, Jun LONG, Xinju FU, Chenguang GAO, Juan YANG, Xu XIA, Yuliang FU, Zhan HU, Xiaoming KANG, Qinqin WU, Aiping PANG, Hongbo ZHOU
2021, 60(1-2):  194-212.  doi:10.13471/j.cnki.acta.snus.2020.11.09.2020B121
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Micro thruster is key to drag free control of space gravitational wave detection task. Based on the micro thruster demand from drag free control system of space gravitational wave detection， the principles of micro thrust technology are analyzed， which lead to the micro thruster satisfying demands including cold gas thruster， wave ionization ion thruster， Cusped field thruster and field emission thruster as alternatives. Their research status and drag free control based on them is also introduced in this paper. Based on this， the developments of Tianqin Plan on these alternatives are introduced thrusters and the future research directions of micro propulsion technologies applied in space gravitational wave detection are prospected.

Key issues in the research on drag-free control for TianQin
Hongyin LI, Xiaorong YE, Jiaheng LIU, Dexuan ZHANG, Ying SHAN, Xin GAO
2021, 60(1-2):  213-224.  doi:10.13471/j.cnki.acta.snus.2020.11.11.2020B129
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Drag-free control technology is to use the thrust generated by the micro-thruster to compensate the non-conservative force on the spacecraft to make it follow the free falling test mass， which is an important way to obtain the ultra-low microgravity level satellite environment， and is one of the key technologies for experimental research in fundamental space physics， microgravity measurement， earth science and space navigation. This paper describes the development history and basic working principle of drag-free control， discusses the composition and control algorithm of the drag-free control system， and finally briefly introduces the structure of the drag-free control system of the TianQin gravitational wave detection mission， and raises key issues and the prospect of future research direction for the research of the TianQin drag-free control system.

Tracking and orbit determination technology of TianQin satellites
Defeng GU, Zicong AN, Yue ZHAO, Chengjun YANG, Kangkang LI, Jubo ZHU, Yuan LIU, Jianing SONG
2021, 60(1-2):  225-232.  doi:10.13471/j.cnki.acta.snus.2020.10.30.2020B108
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The detection of gravitational waves has a high mission demand for satellite orbit determination at the stages of satellites launching into orbits and the operation of scientific experiments. The TianQin project planning to use high orbit satellites， having a greater variety of tracking measurements， the orbit tracking measurement and determination accuracy are influenced by measurement and control distance， measurement system error， formation scale， orbital control， and station tracking geometry， etc. This paper focuses on the tracking measurement and determination technology of TianQin satellite orbit， introducing the requirements of the mission of TianQin satellite orbit determination， analyzing the level and technical characteristics of the various means available for the tracking and measurement of TianQin satellite orbit， and providing an outlook on the development trend of the technology of high-precision TianQin satellite orbit determination.

Review of numerical and hardware-in-the-loop simulation technology of space-borne gravitational wave detection system
Jihe WANG, Yunhe MENG, Jianing SONG, Lu LU, Xin ZHANG, Xing GUO, Jinling ZHOU, Juzheng ZHANG
2021, 60(1-2):  233-238.  doi:10.13471/j.cnki.acta.snus.2020.11.10.2020B124
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Space-borne gravitational wave detection system has the characteristics of ultra-high precision index requirements and strong coupling between subsystems， which makes it difficult for the traditional spacecraft numerical and hardware-in-the-loop simulation technology to be directly applied to the numerical and hardware-in-the-loop simulation verification of space-borne gravitational wave detection system. In order to promote the research of numerical and hardware-in-the-loop simulation technology suitable for space-borne gravitational wave detection system， this paper investigates the research status of numerical and hardware-in-the-loop simulation technology involved in space-borne gravitational wave detection system， including： numerical simulation system， optical/mechanical/thermal/self-gravity multi-field coupling simulation technology， hardware-in-the-loop simulation technology， etc. Then， the key technologies in the numerical and hardware-in-the-loop simulation technology of the space-borne gravitational wave detection system are summarized， including： the architecture design technology of the numerical simulation system of the space-borne gravitational wave detection system， the full task process simulation technology， the high-speed and high-precision multi-field coupling simulation technology， and the hardware-in-the-loop simulation technology of the space-borne gravitational wave detection system with high confidence.

Progress on the design of retroreflector for lunar laser ranging
Qi LIU, Yun HE, Huizong DUAN, Hsienchi YEH, Jiahao XU, Linghao AI
2021, 60(1-2):  239-246.  doi:10.13471/j.cnki.acta.snus.2020.11.06.2020B119
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Lunar laser ranging has made great contributions to the tests of general relativity and the understanding of the Earth-Moon system. However， because of the lunar libration， corner cube retroreflector arrays installed on the Moon about 50 years ago currently limit the laser-ranging precision for a single photon received to centimeter level. Here we mainly introduce the latest progress of developing a 170 mm aperture single and hollow corner cube retroreflector. The measurement shows that three dihedral angle offsets realize 0.10， 0.30， and 0.24 arcsec， respectively. According to the simulation of far field diffraction pattern， this prototype can achieve about 68.5 % optical intensity reflected from ideal Apollo 11 or 14 arrays. We anticipate that this hollow corner cube retroreflector can be applied to the next generation lunar laser ranging.

Research and experiment of lunar laser ranging in Sun Yat-sen University
Tianquan GAO, Caishi ZHANG, Ming LI, Yuqiang LI, Xida HAN, Junxiang LIAN, Shengqian LIU, Zhunbiao LI, Liangcheng TU, Xianlin WU, Shanqing YANG, Xianji YE, Yong YAN, Labao ZHANG, Hongbo ZHANG, Jinxiu ZHANG, Lixiang ZHOU, Yongzhi ZHAO, Hongchao ZHAO
2021, 60(1-2):  247-252.  doi:10.13471/j.cnki.acta.snus.2020.11.11.2020B128
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In order to serve the needs of precise orbit determination for the three satellites of the Tianqin Project， lunar laser ranging analysis and experimental research were carried out. The TianQin laser ranging station in Sun Yat-sen University uses a 1.2 m diameter laser ranging telescope with a laser wavelength of 1064 nm， a laser energy of 320 mJ， a laser repetition frequency of 100 Hz， and a laser pulse width of 80 ps. It also uses a 2×2 multi-element array superconducting detector for lunar laser ranging for the first time. After two years of lunar laser ranging experiments， on the evening of June 8， 2019 （the sixth day of the lunar calendar）， four sets of effective echo signals from the Apollo 15 corner reflector array were obtained for the first time， and then on November 7， 2019 （the tenth day of the lunar calendar）， successfully received effective echo signals from all 5 laser retro-reflector arrays on the lunar surface，with cm level precision， indicating that the TianQin laser ranging station has acquired regular lunar laser ranging capability.